“Antimicrobial Susceptibility Testing for Chlamydia: Out of Sight, out of mind…”

We are fortunate with Chlamydia trachomatis, in that the organism so far, retains almost universal susceptibity to a range of oral antimicrobials, including tetracyclines, erythromycin, azithromycin and even amoxycillin.

This is just as well really as Chlamydia trachomatis is almost exclusively diagnosed by molecular means and antimicrobial susceptibility testing is both difficult and non-standardised.

What we don’t really know about Chlamydia trachomatis is whether continued heavy usage of tetracyclines and azithromycin are leading to “MIC creep” to these antimicrobials. It may be that we only start worrying about this when we start to see treatment failures in significant numbers.

The worry would be that as now Neisseria gonorrhoeae moves towards molecular diagnosis, we will apply the same “out of sight, out of mind” philosophy to this micro-organism. However we definitely cannot afford to go down this route for Neisseria gonorrhoeae as there are already significant resistance problems with this particular bacterium.

We need to remember for both C. trachomatis and N.gonorrhoeae, that just because we aren’t doing susceptibility testing, it doesn’t mean these micro-organisms have suddenly stopped selecting out resistant mutants under antimicrobial pressure….

Michael

p.s. While on the subject of GU microbiology, here is a really nice article on the conditions of cytolytic vagnosis and lactobacillosis, well worth a read.